Enhanced Nitrate-to-Ammonia Efficiency over Linear Assemblies of Copper-Cobalt Nanophases Stabilized by Redox Polymers.

Abstract

Renewable electricity-powered NO3 - reduction reaction (NO3 RR) offers a net-zero carbon route to the realization of high NH3 productivity. However, this route suffers from low energy efficiency (EE, with a half-cell EE commonly <36%), since high overpotentials are required to overcome the weak NO3 - binding affinity and sluggish NO3 RR kinetics. To alleviate this, we suggest a rational catalyst design strategy that involves the linear assembly of sub-5nm Cu/Co nanophases into sub-20nm thick nanoribbons. Our theoretical and experimental studies show that the Cu-Co nanoribbons, similar to enzymes, enable strong NO3 - adsorption and rapid tandem catalysis of NO3 - to NH3 , owing to their richly exposed binary phase boundaries and adjacent Cu-Co sites at sub-5nm distance. In-situ Raman spectroscopy further reveals that at low applied overpotentials, the Cu/Co nanophases are rapidly activated and subsequently stabilized by a specifically designed redox polymer that in situ scavenges intermediately formed highly oxidative NO2 . As a result, we achieve a stable NO3 RR with a current density of ∼450mA cm-2 , a Faradaic efficiency of >97% for the formation of NH3 , and an unprecedented half-cell EE of ∼42%. This article is protected by copyright. All rights reserved.